Yang Z N, Ye X R, Choi S, Molina J, Moonan F, Wing R A, Roose M L, Mirkov T E
Department of Plant Pathology and Microbiology, The Texas A&M University Agricultural Experiment Station, Weslaco 78596, USA.
Genome. 2001 Jun;44(3):382-93.
The citrus tristeza virus resistance gene (Ctv) is a single dominant gene in Poncirus trifoliata, a sexually compatible relative of citrus. To clone this gene, a bacterial artificial chromosome (BAC) library has been constructed from an individual plant that was homozygous for Ctv. This library contains 45,696 clones with an average insert size of 80 kb, corresponding to 9.6 genome equivalents. Screening of the BAC library with five chloroplast DNA probes indicated that 0.58% of the BAC clones contained chloroplast-derived inserts. The chromosome walk across the Ctv locus was initiated using three closely linked genetic markers: C19, AD8, and Z16. The walk has been completed and a contig of ca. 1.2 Mb was constructed. Based on new data, the genetic map in the Ctv region was revised, with Ctv being located between AD8-Z16 and C19 at distances of 1.2 and 0.6 cM, respectively. Utilizing DNA fragments isolated from the contig as RFLP markers, the Ctv locus was further mapped to a region of ca. 300 kb. This contig contains several putative disease-resistance genes similar to the rice Xa21 gene, the tomato Cf-2 gene, and the Arabidopsis thaliana RPS2 gene. This library will therefore allow cloning of Ctv and other putative disease-resistance genes.
柑橘衰退病毒抗性基因（Ctv）是枳（柑橘的一个有性亲和近缘种）中的一个显性单基因。为克隆该基因，已从一株Ctv纯合的单株植物构建了一个细菌人工染色体（BAC）文库。该文库包含45,696个克隆，平均插入片段大小为80 kb，相当于9.6个基因组当量。用五个叶绿体DNA探针筛选BAC文库表明，0.58%的BAC克隆含有叶绿体来源的插入片段。利用三个紧密连锁的遗传标记C19、AD8和Z16启动了跨越Ctv位点的染色体步移。步移已完成，并构建了一个约1.2 Mb的重叠群。基于新数据，修订了Ctv区域的遗传图谱，Ctv分别位于AD8-Z16和C19之间，距离分别为1.2和0.6 cM。利用从重叠群中分离的DNA片段作为RFLP标记，Ctv位点进一步定位到约300 kb的区域。该重叠群包含几个与水稻Xa21基因、番茄Cf-2基因和拟南芥RPS2基因相似的假定抗病基因。因此，该文库将有助于克隆Ctv和其他假定的抗病基因。
